878
FXUS66 KPQR 011715
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1015 AM PDT Mon Jun 1 2026

Updated aviation discussion and watches/warnings/advisories.

&&

.SYNOPSIS...Minimal change in the forecast as all features
appear to be on track. High pressure continues to build through
Tuesday with warming temperatures. Moderate HeatRisk is expected
along the I-5 Corridor north of Salem, including the
Portland/Vancouver Metro. Temperatures cool again to near
seasonable averages by Wednesday as high pressure is replaced
with more zonal flow aloft. Chances for precipitation continues
to decrease with less than a 10% chance now through Thursday.
Cooler conditions likely by next weekend as a low pressure
system in the Gulf of Alaska brings increasing chances for rain
later Friday into Saturday.

&&

.SHORT TERM...Now through Tuesday Night...June 1st and we are
looking at beautiful spring time weather. High pressure and
upper level ridging amplifies offshore with light northeasterly
winds aloft. Will see temperatures rise considerably again today
by around 10 degrees or so within the interior lowlands. There
are varied probabilities of the maximum temperature today
exceeding 85 deg F; the Portland/Vancouver Metro is around 90%,
where as Salem is around 50-60%. HeatRisk is generally "minor"
aside from the direct Portland Metro where HeatRisk is Moderate.
This means that the heat will affect those who are sensitive to
heat, especially those without cooling/hydration. While daytime
highs will be warm, overnight lows will be in the mid to upper
50s. Not quite cold, but cool enough for relief.

Tuesday is the peak of the heat with the high pressure reaching
it`s maximum intensity. The axis of the ridge shifts over
western Oregon Tuesday afternoon. East winds are also expected
to increase out of the Columbia River Gorge Tuesday morning
bringing drier air. The easterly flow combined with downsloping
from the Cascades of the warm temperatures aloft, we will see
even more heating. Expect afternoon temperatures on Tuesday to
rise by around 5-7 deg F with urban areas sitting in the low 90s
and the other inland lowlands closer to 85-90 deg F. Chances for
exceeding 90 deg F are around 30-40% within the interior
lowlands outside of the Portland/Vancouver Metro where the
probability is around 85%. Moderate HeatRisk is much more
widespread shifting into the Lower I-5 corridor and south
towards Salem. Therefore, take precautions on Tuesday if
participating in outdoor activities, especially during peak
afternoon heating. The heat is not expected to last long, though
as a decent marine push is expected by later Tuesday evening
ahead of an upper shortwave trough.

Another consideration is the impact of the offshore flow on both
Monday and Tuesday. This easterly flow will cause humidity to
drop considerably during the day with minimum humidity reaching
the teens in some locations near the mouth of the Columbia River
Gorge. Outside of the coast, cannot rule out humidity around
20-25%. These values are fairly dry for this time of year and
therefore you should refer to your local authorities for any
kind of burning restrictions. -27


.LONG TERM...Wednesday through Sunday...If you have been
tracking the forecast over the last few days, you know that
there is a low pressure system and negatively tilted trough
positioned over the northeast Pacific off of the Alaska
Panhandle. This low will advect cooler air over the region and
enhance onshore flow. However, as has been the trend, each day
this low continues to decay further with each model run.
Therefore the impacts will be minimal in the way of potential
precipitation, but we will see relief from warming temperatures
with high temperatures dropping by around 15 deg F. An
associated frontal band well ahead of the surface low will
approach the coast, but guidance continues to trend down with
minimal, if any, precipitation spreading inland. In fact, NBM
guidance generally shows less than a 10% chance of accumulating
rain through Thursday; except there is around a 20-30% showers
in the Cascades Wednesday afternoon and evening as the afore-
mentioned trough lifts across the region.

Uncertainty increases late in the week and into the weekend
regarding the weakened low pressure system potentially dropping
down from the Gulf of Alaska toward the Washington coast. In
general, there are increasing chances for rain on Friday and
Saturday, but very low chances for any impactful weather.
Ensemble guidance suggests 24-hour rainfall accumulation could
range anywhere from zero (10th and 25th percentiles) up to
potentially exceeding 0.5 to 1.0 inch (closer to the 90th
percentile). Despite the potential pattern discrepancies,
onshore flow is likely which will usher in cooler marine air and
thus lower temperatures. Showers linger through Sunday though
will be light. -27/DH

&&

.AVIATION...Offshore high pressure will begin to move onshore
through the period, supporting continued VFR flying conditions
across the airspace. Largely clear skies aside from few-sct high
cirrus at or above 25 kft will persist through tonight. Diurnal
north to northwest winds will rise by 20-21z Mon to 8-12 kt
inland. Along the coast, winds will reach 10-15 kt with the
frequency of gusts as high as 20-25 kt increasing to the south.
Winds ease below 5 kt out of the north to northeast tonight.

KPDX AND APPROACHES...VFR conditions expected throughout the
period beneath largely clear skies aside from few-sct high
cirrus at or above 25 kft. Diurnal north to northwest winds
will rise to near 10 kt after 20-21z Mon, then ease below 5 kt
by 03-06z Tue. -36

&&

.MARINE...High pressure offshore will continue to generate gusty
north winds through much of Monday. The strongest winds with
gusts up to 25 kt continue south of Cape Falcon, where Small
Craft Advisories remain in effect through 11 PM PDT this
evening. Seas continue at 4-8 ft at 9-10 seconds with a dominant
WNW swell.

Low pressure shifts over the waters on Wednesday causing a
southerly wind reversal on Wednesday. The frontal band along the
leading edge moves over the waters through Wednesday and then
winds shift to the northwest in the post frontal environment.
Unsettled weather continues through the remainder of the week,
with further rain possible next weekend as another front
traverses the waters. A persistent westerly swell will support
continued seas of 4-8 ft at 10-11 seconds. -27/36

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.

WA...None.

PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ252-
     253-272-273.

&&

$$

www.weather.gov/portland

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